Dynamic mass spectrometry was used to characterize the pyrolytic degradation of graphite and carbon black-phenolic resin composites. Measurements were obtained on the overall yield, composition and formation rates of the volatile pyrolysis products. Pyrolysis was found to occur by three general processes: (1) low temperature outgassing of free phenol present in the resin material; (2) formation of water from post-cure reactions at 1%300Β°C; (3) thermal fragmentation of the polymer structure above 350Β°C to yield low molecular weight species. Each of these processes was significantly affected by the presence of the carbon black filler material, with substantially lower yields (< 50%) of volatile products observed. In contrast, the graphite filler appeared to have no effects on resin decomposition. Interaction of the volatile molecular species from he degraded resin with various organic functional groups known to be present on carbon surfaces is suggested as a possible cause for the reduced volatilization observed from carbon black composites. These results suggest that controlled chemical modification of the surface properties of carbon may be employed to increase the char yield from carbon black-phenolic resin composites.